1. Field of the Invention
The present invention relates to moving-picture communication, and more particularly to moving-picture communication through a network of varying bandwidth, and to technology which ensures prescribed image quality by switching between color moving pictures and black and white moving pictures.
2. Description of the Related Art
In moving-picture communication, various technologies have been developed for dynamically adjusting the transmitted data volume in accordance with the bandwidth of the network environment. For example, Japanese Patent Application Publication No. 2002-77857 discloses that re-sequencing and/or selection of the data of respective elements in multimedia data is carried out on the basis of network information relating to the bandwidth, and the corresponding results are stored temporarily in a buffer. The transmission engine processes the multimedia data in accordance with these results, and, for example, omits frames from the video image data, when sending the data to the user terminal.
When video images are exchanged mutually in real time between terminals which are connected through a communications network, such as that in a video telephone and a video conferencing system, there may be a problem in that the video image data has missing frames or the frame rate is lowered if image quality is prioritized (in other words, maintaining a high compressed bit rate in each frame unit). For example, in a video telephone for sign language as used by persons with hearing difficulties, the facial expression and the manual gestures of the other communicating party are important, and if the observer sees a video image of the other party which does not display smooth movement due to missing frames, then it is not possible to recognize the changes in the facial expression, the mouth movements, and the manual gestures, of the other party, and hence it is difficult to understand the contents of the sign language.